Ignition compositions, and preparations and uses thereof

ABSTRACT

An ignition composition comprising a low electron affinity material, an oxidizer and a binder. The ignition composition may be made by A1) preparing a coagulation composition by a shock-gel process using the ingredients of the ignition composition disclosed herein, which comprises: A1-a) dissolving the binder in a low-boiling-point polar solvent to provide a binder solution; A1-b) mixing the low electron affinity material and the oxidizer with the binder solution; and A1-c) adding a low-boiling-point non-polar solvent to the mixture provided by step I-b) to precipitate the binder and form the coagulation composition; and A2) converting the coagulation composition into granular composition using a suitable method.

PRIORITY CLAIM

This application claims the benefit of and priority to U.S. ProvisionalPatent Application No. 61/696,063, titled Ignition Compositions, filedon Aug. 31, 2012, which in incorporated herein by reference thereto.

TECHNICAL FIELD

This invention relates to ignition compositions, including ignitioncompositions usable with decoy countermeasures.

BACKGROUND

Conventional decoy countermeasures for re-entry vehicles rely on chaff,decoy balloons or warhead simulators for long range ballistic missiles.There is a need for an ignition composition that can be used with, amongother things, decoy countermeasures. Novel ignition compositions aredisclosed herein to use pyrotechnic means that can be used alone or inconjunction with other ballistic missile decoy mechanisms for decoycountermeasures.

SUMMARY OF THE INVENTION

One aspect of the application relates to a composition comprising a lowelectron affinity material, an oxidizer and a binder.

Another aspect of the invention relates to methods of preparing theignition compositions disclosed herein.

Another aspect of the application relates to a method of using theignition composition disclosed herein for decoy countermeasures,comprising the following step:

D1) discharging a decoy composition comprising the ignition compositiondisclosed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic graph illustrating Thermogravimetric Analyzer(TGA) analysis (top graph) and ignition composition in an embodiment ofthe present disclosure, as set forth in Example 1, and the graphincludes Differential Scanning Calorimeter (DSC) analysis (bottom graph)of the ignition composition.

FIG. 2 is a burn rate curve illustrating a burn rate analysis of theignition composition according to Example 1.

DETAILED DESCRIPTION

One aspect of the application relates to a composition comprising a lowelectron affinity material, an oxidizer and a binder. In at least oneembodiment, the ignition composition is held together in a granularmatrix formed by the binder, resulting in a pyrotechnic composition thatproduces thrust with an exhaust containing low electron affinitychemical species with high mass flux. This low electron affinityignition composition can be configured using varying quantities of thecomponents such that the mass flux and burn rate can be tailored to meeta desired mass flux and burn time, such as for use as a decoy materialfor re-entry vehicle countermeasures.

In at least one embodiment, the low electron affinity material is ametal. Examples of metal suitable for the ignition composition disclosedherein include, without limitation magnesium (Mg), zirconium (Zr),tungsten (W), tantalum (Ta), aluminum (Al), iron (Fe), manganese (Mn),and other low electron affinity metals. In another embodiment, the lowelectron affinity material is a non-metal (e.g. boron (B)).

Examples of the oxidizer include, without limitation, nitrates (e.g.barium nitrate, or calcium nitrate), perchlorates (e.g. ammoniumperchlorate), and oxides (e.g. CuO). In certain embodiments, theoxidizer does not comprise a salt of alkali metal.

The binder can be an elastomeric binding material that can hold theelectron affinity material and the oxidizer together. Examples of thebinder include, without limitation, rubbers (e.g. Fluorel, acrylicrubbers (e.g. Hytemps), Kraton rubbers or any combinations thereof).

In certain embodiments, the ignition composition further comprises otheradditives such as antioxidant (e.g. A02246(2,2′-Methylenebis(4-methyl-6-tert-butylphenol)), and moisture scavenger(e.g. molecular sieves, preferably in a powder form). In an embodiment,the ignition composition comprises antioxidant of about 0.1% to about0.15% by weight.

As used herein, all ratios of ingredients are by weight. In oneembodiment, the low electron affinity material is about 20% to about 80%of the whole mass of the ignition composition, preferably about 40% toabout 60%. The oxidizer is about 20% to about 80% of the whole mass ofthe ignition composition, preferably about 30% to about 50%. The rest ofthe ignition composition comprises the binder and optionally otherdesired additives. The ratio of ingredients of the ignition compositionis such that the electron affinity of the ignition composition is lessthan about 1 eV.

One advantage of the ignition composition disclosed herein is to providea high mass flux of low electron affinity material desirable for antiballistic missile systems.

In at least one embodiment, the ignition composition includes finelydivided magnesium metal powder, finely divided tantalum metal powder,finely divided barium nitrate, and Fluorel rubber binder blendedtogether using a hi-shear style mixer that results in a granularmaterial after a shock-gel process. In certain embodiments, theresulting mixed ignition composition has a calorific output of about1,250 calories per gram and is stable to about 400° C./752° F. Theignition composition provides a stable burn rate to about 500 psi andwith a burn rate coefficient of less than about 0.5. Burning of theignition composition results in an exhaust wave that has chemicalspecies with low electron affinity and high mass flux that presents atarget for use with anti-ballistic missile systems or othercountermeasure systems.

In another embodiment, the ignition composition has a calorific outputof about 1,200 to about 1,300 cals/gram, a burn rate of less than about0.6 inches/sec at 500 psi, a burn rate exponent is less than about 0.5,and the composition is thermally stable at a temperature as high asabout 375° C./707° F.

Another aspect of the application relates to a method of preparing theignition compositions disclosed herein, comprising the following steps:

A1) preparing a coagulation composition by a shock-gel process using theingredients of the ignition composition disclosed herein, whichcomprises:

A1-a) dissolving the binder in a low-boiling-point polar solvent toprovide a binder solution;

A1-b) mixing the low electron affinity material and the oxidizer withthe binder solution; and

A1-c) adding a low-boiling-point non-polar solvent to the mixtureprovided by step I-b) to precipitate the binder and form the coagulationcomposition; and

A2) converting the coagulation composition into granular composition.

Examples of the low-boiling-point polar solvent in step A1-a) can be,without limitation, a ketone or a mixture of multiple ketones, e.g.acetone, methyl ethyl ketone, or a combination thereof. In certainembodiments, the low-boiling-point polar solvent has a boiling point ofabout 60-98° C. (140-208° F.).

Examples of the low-boiling-point non-polar solvent in step A1-c) canbe, without limitation, a saturated hydrocarbon or a mixture of multiplesaturated hydrocarbons such as isohexane, hexane, heptane or acombination thereof. In certain embodiments, the low-boiling-pointnon-polar solvent has a boiling point of about 60-98° C. (140-208° F.).

In one embodiment, the ratio of polar solvent and the non-polar solventis about 1:3, and the granular pyrotechnic composition yield is greaterthan about 98%.

In another embodiment, all ingredients (solvents, low electron affinitymaterial, and oxidizers) are equilibrated to ambient temperature (e.g.about 20° C./68° F. to about 26° C./78° F.) prior to mixing. Therelative humidity is about 40% to about 70%.

Examples of suitable method in step A2) can be, without limitation,using a hi-shear style mixer, e.g. Cowles, IKA, or Silverson.

In certain embodiments, the mixing step A1-b) occurs in a hi-shear mixer(e.g. Cowles, IKA, or Silverson). The low electron affinity material andthe oxidizer may be added into the binder solution at the same ordifferent time. In one embodiment, the low electron affinity material isfirst added into the binder solution and mixed for about 10 minutes toabout 15 minutes, and then the oxidizer is added into the solution andmixed for about 10 minutes to about 15 minutes.

In another embodiment, the method of preparing the ignition compositionsfurther comprises steps A1-d) and A1-e) after step A1-c) and before stepA2):

A1-d) decanting the solvents from the mixture obtained from step A1-c);and

A1-e) drying the obtained coagulation composition to a constant weight.

In certain embodiments, step A1-e) is performed at a temperature higherthan room temperature (e.g. about 70° C./158° F.).

Another aspect of the application relates to a method of preparing theignition compositions disclosed herein using a static mixer, comprisingthe following steps:

B1) introducing a first stream of binder/polar solvent/low electronaffinity material/oxidizer mixture to the static mixer;

B2) intersecting the first stream in step B1) with a second stream ofnon-polar solvent in the static mixer; and

B3) forming granules of the ignition compositions through the turbulenceof the static mixer.

In certain embodiments, the method of preparing the ignitioncompositions further comprises steps B4) and B5) after step B3)described above:

B4) decanting the solvents from the mixture obtained from step B3); and

B5) drying the obtained granule composition to a constant weight.

Step B5) may be performed at a temperature higher than room temperature(e.g. about 70° C./158° F.).

Examples of polar solvent and non-polar solvent are the same asdescribed above.

In one embodiment, the ratio of polar solvent and the non-polar solventis about 1:3, and the granular pyrotechnic composition yield is greaterthan about 98%.

In another embodiment, all ingredients (solvents, low electron affinitymaterial, and oxidizers) are equilibrated to ambient temperature (e.g.about 20° C./68° F. to about 26° C./78° F.) prior to mixing. Therelative humidity is about 40% to about 70%.

Another aspect of the application relates to a method of preparing theignition compositions disclosed herein, comprising the following steps:

C1) mixing all ingredients of the ignition composition using a mixer;and

C2) granulating the mixture obtained from step C1.

Examples of mixers that can be used in this method include, withoutlimitation, Simpson Mix-Muller and VibroAcoustic® Mixers, and mixersworking with similar mixing mechanisms. For example, Simpson Mix-Mullermixes the components using a wheel/scraper mechanism, and Resodyn VibroAcoustic® mixer uses vibrations to create mixing on a micro scalewherein the composition components are placed into a mixing containersealed and placed upon the mixer to go through a prescribed routine.

In certain embodiments, the method of preparing the ignitioncompositions further comprises step C3 after step C2) described above:

C3) drying the obtained granule composition to a constant weight.

Step C3) may be performed at a temperature higher than room temperature(e.g. about 70° C./158° F.).

In another embodiment, all ingredients (solvents, low electron affinitymaterial, and oxidizers) are equilibrated to ambient temperature (e.g.about 20° C./68° F. to about 26° C./78° F.) prior to mixing. Therelative humidity is about 40% to about 70%.

Another aspect of the application relates to a method of using theignition composition disclosed herein for decoy countermeasures,comprising the following step:

D1) discharging a decoy composition comprising the ignition compositiondisclosed herein.

In one embodiment, the decoy composition provides radar signatures toconfound interceptor threats to vehicles upon atmospheric reentry. Inanother embodiment, the decoy composition is used for missile defensesystems training.

In another embodiment, the ignition composition disclosed herein is usedalone for decoy countermeasures. In another embodiment, the ignitioncomposition disclosed herein is used with one or more other ballisticmissile decoy mechanisms (e.g. chaff, decoy balloons, warhead simulatorsand/or electronic countermeasures) for decoy countermeasures.

The following provides one or more examples related to the ignitioncomposition in accordance with embodiments of the present disclosure:

Example 1. Magnesium-barium nitrate composition:

A composition was prepared to have 56% Mg (by weight) (˜400 atomized),39% Ba(NO₃)₂, and 5% Fluorel (using 25% solution in acetone) accordingto the method described herein.

1. Mg and Ba(NO₃)₂ were checked for moisture content and if greater than0.05% moisture they were dried to constant weight at 70° C./158° F.

2. Flourel stock solution in acetone (25% by weight) was prepared bymixing the appropriate amount of Flourel solid with acetone.

3. Solvent was equilibrated to mix bay temperature, typically 21° C./70°F. at relative humidity 40-70%.

4. Mixing Process:

-   -   I. Flourel solution was added to the mix bowl and Ba(NO₃)₂ was        added and agitated for about 10-15 minutes.    -   II. Mg was added to the mix bowl and agitated for about 10-15        minutes.    -   III. Isohexane was added to the mix bowl with agitation to        precipitate the composition granules out of solution, after        complete solvent addition agitation continues for 1-2 minutes.    -   IV. The solvents were decanted and the granules were rinsed with        fresh isohexane and solvents were decanted.    -   V. The pyrotechnic composition was dried to constant weight at        70° C./158° F.

The dried pyrotechnic composition was subjected to calorific output,burn rate, and TGA/DSC testing.

The performance of the ignition compositions were carried out usingPropellant Evaluation Program (PEP).

The resulting ignition composition had a calorific output of about1,200-1,300 calories per gram. Thermogravimetric Analyzer (TGA) analysisshowed that the ignition composition was stable to about 400° C./752° F.(FIG. 1, top graph). Differential Scanning Calorimeter (DSC) analysis ofthe ignition composition showed two peaks at about 500° C./932° F. andabout 570° C./1058° F., showing the thrust capability of the ignitioncomposition (FIG. 1, bottom graph).

The ignition composition was tested for burn rate at the pressure ofabout 200 psi to about 500 psi using conventional methods. For example,composition burn rate was determined by pressing a pellet of thepyrotechnic material to provide a sample that can be burned only on theignition face and not on the sides (i.e. to produce a “cigarette burn.”)The sample was placed in a Crawford style test bomb that was pressurizedto the desired test pressure. Several samples were tested at eachpressure and a regression analysis was conducted. The results indicateda stable burn rate to about 500 psi and showed a burn rate coefficientof less than about 0.5 (FIG. 2).

The results showed that the ignition composition had desired propertiesto provide a high mass flux of low electron affinity material with athrust capability, and can be used for anti ballistic missile systems.

From the foregoing, it should be appreciated that specific embodimentsof the disclosure have been described herein for purposes ofillustration, and not for limitation. Various modifications may be madewithout deviating from the spirit and scope of the disclosure.Furthermore, while various advantages associated with certainembodiments of the disclosure have been described above in the contextof those embodiments, other embodiments may also exhibit suchadvantages, and not all embodiments need necessarily exhibit all suchadvantages to fall within the scope of the disclosure.

I/we claim:
 1. An ignition composition comprising a low electronaffinity material, an oxidizer and a binder.
 2. The ignition compositionaccording to claim 1, wherein the low electron affinity material isselected from the group consisting of boron (B), magnesium (Mg),zirconium (Zr), tungsten (W), tantalum (Ta), aluminum (Al), iron (Fe),and manganese (Mn).
 3. The ignition composition according to claim 1,wherein the oxidizer is selected from the group consisting of nitrates,perchlorates, and oxides.
 4. The ignition composition according to claim3, wherein the oxidizer is selected from the group consisting of bariumnitrate, calcium nitrate, ammonium perchlorate, and CuO.
 5. The ignitioncomposition according to claim 1, wherein the binder is selected fromthe group consisting of Fluorel, acrylic rubbers, Hytemps, Kratonrubbers, and any combinations thereof.
 6. The ignition compositionaccording to claim 1, further comprising additives selected from thegroup consisting of antioxidants, moisture scavengers, and combinationsthereof.
 7. The ignition composition according to claim 6, wherein theignition composition comprises antioxidant of about 0.1% to about 0.15%by weight.
 8. The ignition composition according to claim 6, wherein theantioxidant is A02246 (2,2′-Methylenebis(4-methyl-6-tert-butylphenol).9. The ignition composition according to claim 6, wherein the moisturescavenger is molecular sieves.
 10. The ignition composition according toclaim 1, wherein the electron affinity of the ignition composition isless than 1 eV.
 11. A method of making the ignition compositionaccording to claim 1, comprising: A1) preparing a coagulationcomposition by a shock-gel process using the ingredients of the ignitioncomposition disclosed herein, which comprises: A1-a) dissolving thebinder in a low-boiling-point polar solvent to provide a bindersolution; A1-b) mixing the low electron affinity material and theoxidizer with the binder solution; and A1-c) adding a low-boiling-pointnon-polar solvent to the mixture provided by step I-b) to precipitatethe binder and form the coagulation composition; and A2) converting thecoagulation composition into granular composition using a suitablemethod.
 12. The method according to claim 11, wherein thelow-boiling-point polar solvent is a ketone or a mixture of multipleketones.
 13. The method according to claim 11, wherein thelow-boiling-point nonpolar solvent is a saturated hydrocarbon or amixture of multiple saturated hydrocarbons.
 14. The method according toany of claim 11, wherein the ratio of polar solvent and the non-polarsolvent is about 1:3.
 15. A method of preparing the ignition compositionaccording to claim 1 using a static mixer, comprising the followingsteps: B1) introducing a first stream of binder/polar solvent/lowelectron affinity material/oxidizer mixture to the static mixer; B2)intersecting the first stream in step B1) with a second stream ofnon-polar solvent in the static mixer; and B3) forming granules of theignition compositions through the turbulence of the static mixer. 16.The method according to claim 15, wherein the low-boiling-point polarsolvent is a ketone or a mixture of multiple ketones.
 17. The methodaccording to claim 15, wherein the low-boiling-point nonpolar solvent isa saturated hydrocarbon or a mixture of multiple saturated hydrocarbons.18. The method according to claim 15, wherein the ratio of polar solventand the non-polar solvent is about 1:3.
 19. A method of preparing theignition composition according to claim 1, comprising the followingsteps: C1) mixing all ingredients of the ignition composition using amixer; and C2) granulating the mixture obtained from step C1.
 20. Amethod of using the ignition composition according to claim 1 for decoycountermeasures, comprising discharging a decoy composition comprisingthe ignition composition.
 21. The method of claim 20, wherein theignition composition is used with one or more other ballistic missiledecoy mechanisms.
 22. The method of claim 21, wherein the one or moreother ballistic missile decoy mechanisms are selected from the groupconsisting of chaff, decoy balloons, warhead simulators and electroniccountermeasures.